The development of wireless charging allows a portable electronic device, such as a mobile phone, a MP3 audio/video playing device, and a digital camera, to carry out power transmission and receiving through adoption of a wireless power receiving device. A user of the electronic device, when located outdoors, does not need to locate a wall outlet of an electric main before he or she can charge an exhausted battery of the electronic device. A conventional wireless charging device has a power receiving device that is often set inside an enclosure of a device that is powered by the battery to be charged, such as a receiving device of a wireless charging device for mobile phone battery. Such an arrangement causes a problem that the device enclosure is often made of a material comprising ferrous materials or aluminum or metal electroplating layers, which shield the transmission of wireless charging signals, thereby deteriorating the performance of wireless charging. As a consequence, the wireless charging cannot be widely accepted.
Thus, the present invention aims to provide an externally attachable wireless charging device for overcoming the above problems.